Spark plug electrode



Patented Apr. 3, 1934 un ts!) STATES PATENT "OFFICEY SPARK PLUG ELECTRODE Ohio No Drawing. Application May 1, 1931,

Serial No. 534,463 f 6 Claims.

This invention relates to sparlcplug electrodes.

When an electric current is passed to or from a spark plug electrode of an internal combustion engine or the like, a disintegration of the electrode occurs resulting in time in completely destroying the material thereof. A spark plug electrode is subjected not only to high temperatures but also to the action of chemical and physical agencies, this effect being particularly noticeable and objectionable when tetra-ethyl lead is used in the gasoline forming a charge. The corrosion and erosion caused in the highly heated atmosphere surrounding the electrode by metallic lead, lead oxides, halogen lead compounds, halogen acids, and sulfuror sulfur compounds is very great. The rapid flow of the gas carrying these compounds increases the rateoi deterioration. Also the acid products of combustion or the acid products produced by the hydrolysis of combustion deposits readily attack the electrode both in the zone of the arc, and outside thereof to further disintegrate the same.

It is an object of the present invention to provide an electrode which will to a great extent overcome the defects and disadvantages mentioned, and which can withstand high tempera- The material which, according to the present invention, is used for forming a spark plug electrode that is adapted to resist the deteriorating effects of corrosion and erosion comprises a ferrous base and certain additive materials, one of'which is chromium.

Chromium should be present in amounts varying from approximately 6% to 18%. These and other percentages are given as illustrative of the preferred range of the several elements only, and it will be understood that the limits may be extended somewhat and the resulting alloy will still retain substantially the desired corrosion resisting properties. Chromium and iron alone do not produce a satisfactory material for spark plug electrodes but certain additional material, which varies from approximately 8% to 44% is added to render the electrode corrosion and erosion resisting. As one example of this material, nickel may beadded, varying in amounts from 8% to 30%. In addition to nickel, tungsten or, alternately, molybdenum-in amounts up to 6% may be added, and if desired, silicon up to 4%.

One composition which has been found to give very satisfactory results consists of 12% chromium, 12 nickel, and 2%% of tungsten, the remainder being iron. A second example comprises 12% chromium, 20% nickel, and 2 tungsten. In each of these examples the tungsten can be replaced by molybdenum with very satisfactory-results.

Instead of adding nickelyin addition to the chromium, a corrosion resisting alloy may also 7 comprise the addition of 2% to 10% aluminum and 3% to 6% silicon. The composition of one such material is 6% to 13% chromium, 7% to 10% aluminum, 3% to 6% silicon and the remainder iron.

Numerous tests have demonstrated that electrodes formed of the compositions set forth above have greatly increased corrosion and erosion resisting properties, and are particularly adapted for use with ethyl gasoline which has little deteriorating effect upon such electrodes. Where other electrode materials become coated with oxide and scale, and even disintegrate under the conditions obtaining in the cylinder of an internal combustion engine, the materials of the present invention remain clear, smooth and practical- 1y uncoated with oxide over very long periods of use. They offer greatly improved resistance to erosion by the electric arc with current values emlead oxides, halogen lead compounds,- halogen acids, and free sulfur or sulfur compounds. The reduced rate of erosion may be due, in part, to a reduction in the eating away of the opposed electrode surfaces between which the arc passes as a result of improved resistance to condensed acidv product of combustion of gasoline or acid products produced by the hydrolysis of deposits resulting from combustion.

By means of the composition of this invention, the construction of spark plugs can be greatly simplified and the costreduced while at the same time their period of life may be extended. As new constructed spark plugs ordinarily are made up of a core electrode, a core spindle, anda core spindle head, of different metals. By using a material of the present invention for all these parts or for the core electrode and either of the other parts, the, entire core structure may be simplifled and made integral without increasing the cost .of the spark plug. Similarly, the shell, which now ordinarily is made of one metal and the side electrode of another, may also be made entirely of this inexpensive material with a consequent reduction in the manufacturing cost. Heretofore such alloys as have been suitable for electrodes have been so expensive as to prohibit their use for forming the entire spark plug structure therefrom. The present invention provides a material extremely resistant to corrosion and erosion which at the same time'is relatively inexpensive so that all of the parts of the spark plug may be constructed thereof and the usual expense of assembling the several portions of shell and core eliminated. V v

While the materials herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise compositions, and that changes may be made therein without departing fromthe scope of the invention whiclr'is defined in the appended claims. l

Whatfis claimed is:

1. A spark plug electrode adapted to resist corrosion and having improved resistance to erosion by the electric are when the atmosphere surrounding the electrodes contains leads, lead compounds, halogen compounds or sulfur comprising a ferrous base having 6% to 13% chromium, and 8% to 30% nickel.

2. A corrosion and erosion resisting spark plug electrode comprising a ferrous base having 6% to 18% chromium, 8% to 30% nickel, and not more than 6% tungsten.

3. A corrosion and erosion resisting spark plug electrode comprising a ferrous base having 6% to 18% chromium, 8% to 30% nickel, not more than 6% tungsten, and not more than 4% silicon. 4. A corrosion and erosion resistant spark plug having its shell, shell electrode, and core electrode made of a ferrous base alloy containing 6% to 18% chromium, 8% to 30% nickel, 0% to 6% tungsten, 0% to 4% silicon.

5. A spark plug electrode'having improved corrosion and erosion resistance to condensed acid products of combustion of gasoline comprising a ferrous base alloy containing 6% to 18% chromium and 8% to 30% nickel;

6. A spark plug electrode adapted to resist corrosion and having improved resistance to erosion by the electric are when the gas surrounding the electrode contains lead, lead compounds, halogen compounds or sulfur comprising a ferrous base alloy containing 6% to 18% chromium, 8% to 30% nickel and not over 4% silicon.

SAM D. HERON. 

